This research focuses on cytoskeletal elements of frog olfactory axons, with emphasis on microtubules. The three-dimensional relationships between axoplasmic microtubules and neutrofiliments will be studied with the electron microscope. Cytochemical tests will be used on the ultrastructural level to localize ATPase activity in olfactory axons, and since some axons contain only neurofilaments and no microtubules, it will be of interest to see if these show ATPase activity distributed in the same manner as in axons containing both neurofilaments and microtubules. The substructure of isolated neurofilaments and neurofilaments in situ will be studied. Homogenates of olfactory nerve will be examined by SDS disc and slab gel electrophoresis to characterize the kinds of proteins present, particularly cytoskeletal proteins. Studies of the polarity of axonal microtubules will be continued, and these will involve the addition of soluble tubulin to preexisting microtubules as ribbon elements whose cross-sectional curvature indicates the polarity of the microtubules to which they are attached (ribbons either curve clockwise or counterclockwise). Finally, tracer studies will be used to test the hypothesis that bidirectional transport occurs in olfactory nerve axons, and these findings will be related to evidence regarding microtubule polarity.